Biogeography

The theory developed by MacArthur and Wilson (1967) that species richness on an island is determined by a dynamic equilibrium between the rate of immigration of new species and the rate of extinction of established species. Island size and distance from the mainland are the primary controlling variables.

The separation of a continuously distributed ancestral population into geographically isolated groups by the formation of a physical barrier such as a mountain range, a seaway, or a rift valley. Over time the isolated populations may diverge into distinct species.

The movement of organisms from their place of origin to a new area, often crossing a pre-existing barrier. Dispersal events can be active (self-propelled) or passive (carried by wind, water, or other organisms) and can lead to colonization of new habitats.

The state of a species or other taxonomic group being found exclusively in a particular geographic area and nowhere else in the world. High levels of endemism typically result from long geographic isolation or unique environmental conditions.

A large-scale community of organisms defined primarily by the dominant vegetation type and characterized by adaptations to a particular climate. Biomes are distributed across the globe in predictable patterns tied to latitude, altitude, and precipitation regimes.

One of the major divisions of the Earth's surface based on the evolutionary history and taxonomic composition of its flora and fauna. The classical system recognizes realms such as the Nearctic, Neotropical, Palearctic, Afrotropic, Indomalayan, and Australasian.

The empirical observation that larger areas support more species, commonly expressed as S = cA^z, where S is species number, A is area, and c and z are constants. This is one of the most robust patterns in ecology.

The pattern in which species richness increases from the poles toward the equator. This is the most widely recognized biodiversity pattern on Earth, observed in nearly all major taxonomic groups, though its causes remain actively debated.

Geographic areas where populations of organisms survived periods of unfavorable conditions, such as glaciations, that eliminated them from surrounding regions. Refugia serve as centers from which species recolonize when conditions improve.

A biogeographic boundary running through the Malay Archipelago between Bali and Lombok and between Borneo and Sulawesi, marking a sharp transition in faunal composition. Species west of the line have Asian affinities, while those to the east have Australasian affinities.